<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>

    <style>

        /* div{width: 200px; height: 100px; background-color: red;
            margin-right: auto;
        } */
/* 
        #box1{width: 300px; height: 300px; background-color: red;} */
        /* #box2{width: 100%; height: 100px; background-color: blue; padding-left: 30px; border: 10px solid green;} */

        /* #box2{height: 100px; background-color: blue; padding-left: 30px; border: green 5px solid; } */



        /* 练习 */
        #div1{
            background-color: white;
            border-style: dashed;
            border-width: 1px;
            border-color: black;
            width: 300px;
            height: 300px;
        }

        #div2{
            background-color: rgb(123, 123, 180);
            border-style: solid;
            border-width: 2px;
            border-color: rgb(61, 61, 231);
            width: 250px;
            height: 250px;
            margin: 0 auto;
            margin-top: 25px;
        }

        #div3{
            background-color: magenta;
            width: 200px;
            height: 200px;
            margin: 0 auto;
            margin-top: 25px;
        }

        
    </style>


</head>
<body>

    <!-- <div id="box1">
        <div id="box2">哈哈哈哈</div>

    </div> -->
    

    <div id="div1">
        <div id="div2">
            <div id="div3"></div>
        </div>
    </div>


</body>
</html>